1. Field of the Invention
This invention relates generally to a signal processor for processing a color video signal of the kind in which crosstalk components of a luminance signal and a color carrier signal from tracks adjacent the track being reproduced are frequency-interleaved relative to the respective luminance and color carrier signal in the track being reproduced and, more particularly, to a signal processor using a comb filter for removing these crosstalk components.
2. Description of the Background
Video tape recorders for recording and reproducing video signals of the kind using a half-inch magnetic tape are now well known for home use. Typically, when recording, the video signal is separated into luminance and color carrier signals and the color carrier signal is frequency down-converted to place it on the low side of the luminance signal in the frequency spectrum and by use of the so-called phase inversion technique or phase shift technique the frequency of the color carrier is further converted so that the crosstalk components from adjacent tracks have a frequency-interleaved relationship with the signal from the track being reproduced. This is intended to aid in crosstalk cancellation. The luminance signal has the DC level normally contained in the broadcast signal cancelled therefrom and is then frequency modulated and frequency shifted by 1/2 the horizontal frequency every other track, whereby the luminance crosstalk component from the adjacent tracks upon reproduction will have a frequency-interleaved relationship with the luminance signal in the track being reproduced. As in the case of the chrominance or color carrier signal, such frequency interleaving is intended to aid in eliminating the unwanted crosstalk components. This known approach typically requires two comb filters, each of which requires at least dedicated delay line, generally having a time delay of one horizontal scan, and the frequency-interleaved relationship means that during reproduction of the recorded color video signal such crosstalk components can be removed by using comb filters. A comb filter is well known and is a filter having an insertion loss that forms a sequence of narrow passbands, or narrow stopbands, that are centered at multiples of some specified frequency. In most generally known systems, in order to reproduce color video signals and to eliminate the crosstalk components from adjacent tracks at least two comb filters are required.
The unwanted crosstalk components can be removed using the known comb filters, however, time delay circuits of one horizontal scan time delay are very expensive to fabricate and are of a relatively large size compared with other circuit elements in the overall video signal processing assembly. Additionally, one comb filter is required for each of the luminance signal and the color carrier signal (chrominance), thereby exacerbating the problem by increasing the manufacturing costs and the increasing the space requirement for mounting the circuitry. Typically, individual delay lines are required in the recording circuitry for processing the signals for recording, however, if in place of a conventional delay line a charge coupled device (CCD) is used, which has a suitably broad frequency range to encompass both the luminance signal as well as the color carrier signal, then the time delay operations involved can be accomplished simultaneously. Nevertheless, upon reproduction regardless of the kind of time delay circuits employed, a separate, dedicated comb filter is necessary for the luminance signal and the color carrier signal.
Although there have been proposed systems to accomplish cancellation of the crosstalk components of the luminance and color carrier signal using only a single delay circuit, in order to carry out other signal processing operations, such as noise removal and cancellation and the like, it still remains necessary to utilize another comb filter to separate the luminance and chrominance signals.